There are specific physical candidates that may explain the difference, for
example volcanic activity, proper representation of ocean temperatures, and variability in ocean processes.
Not exact matches
Unlike microcrystals, for
example, the tubules have complex forms — often observed abruptly changing direction to avoid intersecting each other, in a manner consistent with tunneling microbial behavior — and contain organic molecules associated with biological
activity; the Ries tubules are also similar to fossil traces of microbes found in
volcanic glass.
For
example, I didn't see much green taking hold within the area of Olympus Mons and the surrounding volcanoes, both due to the
volcanic activity and the proximity to the equator,» Gill says.
The waters around the island of Ischia in Italy, for
example, have been acidified for a long time because there is the Vesuvio volcano nearby; there are a lot of
volcanic activities and CO2 sources, that is there is CO2 from the bottom to the surface, which is acidifying the water.
A good
example of this is obsidian — a beautiful, naturally occurring compound that is formed during
volcanic activity.
Visitors interested in the geology of the area don't have to look too hard to find excellent and diverse
examples of
volcanic activity.
He gave as an
example the «energy sent by the sun and
volcanic activity that spits out lava and enormous quantities of substances in the atmosphere.»
For
example, reconstructions suggest decreased solar
activity and increased
volcanic activity in the 17th century as compared to current conditions.
So, for
example, if we go through a period of relative higher solar output, and less
volcanic activity, relatively less cloudiness, and higher greenhouse gas levels, these would all tend to increase ocean heat content.
The same models that are valid today would be valid, for
example, through periods of much higher
volcanic activity, different geographic arrangements and foliage (albedo), and different atmospheric composition.
One
example of where relatively small changes to geological stress can have a big impact on
volcanic activity is the Pavlov volcano in Alaska.
For
example very powerful
volcanic activity in the past are numerous and well known, also we evidence of huge impactors which have hit earth.
The catch is the degree of magnitude change and duration of time of the solar variations must reach certain LEVELS in order to overcome the inherent negative feedbacks in earth's climatic system, along with natural earth bound random climate events (
examples enso,
volcanic activity).
Alternative explanations are available, for
example that climatic changes are responsible for changes in continental ice mass that affect
volcanic activity.